This invention relates to a cryogenic expansion engine. In more detail the invention relates to a reciprocating expansion-engine refrigerator for cooling helium to a low temperature.
Large quantities of liquid helium are required for cooling superconducting magnets employed in particle accelerators. Helium can be liquified with refrigeration systems using a Joule Thompson valve with an expansion engine. In such devices a valve is opened allowing high pressure low temperature helium gas to enter a cylinder and expand against a piston causing the piston to move. During this movement the gas expands in the cylinder lowering pressure and temperature. Another valve then opens and the return motion of the piston forces the cooled gas out of the cylinder for further cooling and liquification.
Cryogenic expansion engines have a history of high maintenance and difficulty in matching engine performance with refrigerator components. The cryogenic expansion engine described herein is particularly useful in a system for liquefying large quantities of helium because of ease of maintenance and easy adjustability of the valve action.